The Airbus A350. Credit:Airbus
A carbon fibre-reinforced high-performance polymer (CFRP) has been selected by Airbus Helicopters to replace aluminium in an aircraft door fitting of the Airbus A350-900. The decision is said to both improve component quality and reduce weight and costs by 40 percent.
The A350-900 is one of the three models in the family of Airbus’ new, wide-body passenger aircraft, known as A350-XWB. The new generation jetliners, are said by the aircraft manufacturer to be “setting a new standard of efficiency” with 25 percent lower fuel consumption compared to competitor models, more passenger comfort and more room.
The fibre-reinforced polymer (FRP) structure of the A350-XWB’s aircraft door uses an outer skin coupled with a bracing structure on the inside. A fitting, manufactured from Victrex’s PEEK 90HMF40 thermoplastic, connects the outer skin to points on the internal bracing structure. The two components form a box-type structure to exploit the maximum geometrical moment of inertia.
Christian Wolf, Head of Aeroplane Doors Research and Technology, Airbus Helicopters, explained the operation and significance of the PEEK component: “In terms of the standard load case, i.e. the internal cabin pressure, this point-type joint reduces the deformation on the outer skin, thereby maintaining the aerodynamic quality of the aircraft door. All components in the aircraft door are of a singly redundant design. If a component near the bracket fails, the bracket will provide an alternative path for transferring structural loads and is therefore part of the aircraft’s primary structure.”
Metal replacement: New bracket reduces costs and improves quality
By using the carbon fibre-reinforced high-performance Victrex PEEK 90HMF40 polymer instead of the aluminium previously used, Airbus Helicopters has successfully manufactured an equivalent component that provides a range of benefits, in addition to reducing weight and production costs by 40 percent. These include joining the PEEK component, instead of an aluminium component, to a thermoset, resulting in making drilling much easier, as well as optimised carbon-fibre-reinforced plastic (CFRP) drills that have improved the quality of the holes compared with the previous solution.
Victrex PEEK 90HMF40 is a material specified by Airbus. The thermoplastic is said to easily withstand the moisture that continuously accumulates inside aircraft doors, whereas aluminium, which is prone to corrosion, needed a special surface coating to prevent corrosion. “The suitable material, supplied by Victrex, as well as their expertise and collaboration with their materials experts have contributed to the successful development and component qualification. The expertise gained from the initial use of fibre-reinforced PEEK can be transferred to other components and to other areas of application with similar requirements”, added Wolf.
New developments and investments help maintain the lead
In the aerospace business the ‘design and build’ process, e.g. development in accordance with a given specification, is a possible option for producing structural components. In this process, the developer has additional freedom in matters such as the selection of materials. “90HMF40 is a special high-performance thermoplastic which is also suitable for load-bearing structural components, as now used for the first time in the Airbus A350-900 and therefore in regular airline operations. This first application is certain to be quickly followed by others”, explained Uwe Marburger, Aerospace Business Development Manager at Victrex.
Victrex PEEK 90HMF40 is a high-performance polymer with high-modulus fibres (HMF). It is based on the Victrex 90-Series polyaryletherketone, which is primarily used in very thin-walled injection-moulded components. High-strength components can be manufactured from material, whose properties include up to 100 times longer fatigue life and up to 20 percent greater specific strength and stiffness than aluminium 7075-T6 when performing under the same conditions.